This piece is directed at CFIs, but failing to intervene when an accident is imminent isn't a CFI-specific problem. It happens with big air carriers (see Asiana 214), and it happens even when we're not flying. If you send a dependable subordinate an email asking them to do a job, there's a good chance it'll get done. If you email two dependable subordinates asking that one of them do a job, the odds of it getting done go way down.
Crew resource management (CRM) training is required for some commercial operators (see AC 120-51E), but bad CRM can rear its head anytime you're in an airplane with more than one set of controls. Until you've been expressly overruled by the PIC, you (from post-solo student on up) are always responsible for the safe outcome of the flight.